Path: utzoo!mnetor!uunet!lll-winken!lll-tis!ames!ncar!boulder!sunybcs!rutgers!aramis.rutgers.edu!athos.rutgers.edu!hedrick From: hedrick@athos.rutgers.edu (Charles Hedrick) Newsgroups: comp.dcom.lans Subject: Re: Ethernet utilisation Message-ID: Date: 3 May 88 02:15:53 GMT References: <47@xenon.UUCP> Organization: Rutgers Univ., New Brunswick, N.J. Lines: 18 Keywords: ethernet csma/cd utilisation To: goodloe@xenon.UUCP I saw the Ethernet work as Xerox PARC working papers, but Bertsekas and Gallaher reference an article by Metcalfe and Boggs, "Ethernet: Distributed Packet Switching for Local Computer Networks", Commun. ACN [sic - presumably ACM], 395-404. As I recall, the Xerox studies claimed 90% loading. We've heard recently from Van Jacobson that he has gotten over 8MB/sec sustained throughput on an FTP transfer over an Ethernet. Of course this is probably more than 80% Ethernet utilization because of various network overheads. On the other hand, I don't think you'd want to load a network to even 50%. General statistical rules of thumb suggest that when you've got lots of users contending in a random way, your peaks are going to be an order of magnitude above your average, so in order to avoid slowing people down when they need bursts of speed (which is quite typical in the normal Ethernet applications), you don't want steady state loading (i.e. averages over a minute or so) to be above 10%, even during your peak periods. The same consideration would be true for token ring or any other type of medium. That is, the effects due to the very random character of the traffic are likely to dominate the effects due to differences between CSMA, token ring, etc.